#define _CRT_SECURE_NO_WARNINGS 1
class Solution {
public:
    void reverseString(vector<char>& s) {

        int n = s.size();
        int left = 0, right = n - 1;
        while (left < right) {
            char tmp = s[left];
            s[left] = s[right];
            s[right] = tmp;
            left++;
            right--;
        }

    }
};